I have a thornless blackberry bush with a vine growing into one thick 3-inch vine with lots of leaves and no fruit. The other vines have fruit. What kind of a growth do I have?
Certified GKH Gardening Expert
This sounds like a witches broom. They have many causes. This article will explain more: https://www.gardeningknowhow.com/ornamental/trees/tgen/witches-broom-disease.htm